James Watt, a Glasgow scientific instrument maker, is famed as the inventor of a new, more efficient steam engine. Watt’s success, however, was not simply a reflection of his ingenuity, but was rooted in eighteenth-century Scotland’s involvement in the Atlantic slave economy. His father was a Greenock West India merchant who occasionally traded in enslaved people. Although Watt personally condemned chattel slavery as ‘disgraceful to humanity’, his company later sold many engines to Caribbean plantations, maintaining their profitability at the very time the slave trade was being criticised and then abolished.